PEEISSODACTYLA. 
255 
The canines are large and curved, and much produced upward and 
slightly outward from the alveolar border. The crown is subacute, with 
an oval section at the base, and smooth enamel. The first premolar is about 
equidistant between the base of the canine and that of the second premolar. 
Its crown is lenticular in section, with a cutting-edge fore and aft, and no 
tubercles or cingula. The second premolar possesses a rudimental anterior 
basal tubercle; it has no external basal cingulum. There is a rudimental 
cingulum on the outer side of the heel of the third premolar, and an inter¬ 
rupted one on the outside of the fourth. The true molars possess an 
uninterrupted basal cingulum on the outer side. The heel of the last molar 
is Mude; the root supporting it is continuous with that which supports the 
middle of the crown. The enamel is eveiywhere smooth. 
Measurements. 
M. 
Length from the incisive border to the end of the last molar. 0.075 
Length from the incisive border to the first premolar. 0. 020 
Distance between the first and second premolars. 0.007 
Length of six posterior molars...... 0.045 
Length of three true molars.. 0. 027 
Diameter of the canine... 0. 005 
Width of the fourth premolar posteriorly. 0. 005 
Width of the second true molar.... 0. 000 
Length of the third true molar.. 0. 0116 
Width of the same...... 0. 0055 
Depth of the ramus in front of the first premolar. 0.009 
Depth of the ramus at the first true molar ..... 0. 015 
Width of the symphysis at the front of the diastema .... 0. 014 
The simplicity of tbe anterior inner cone of the molar teeth distinguishes 
this species from the two that follow. 
Orotherium vintanum, Marsh. 
Plate Ixv, figs. 1-12. 
Amer. Jour. Sci. and Arts, 1872 {separata^ p. 26). 
In the specimen of this animal already alluded to in the description of 
the genus, the true molar teeth of both jaws with numerous bones of the 
skeleton are preserved. These I found lying together at the base of a 
bad-land bluff, and as there is no admixture of incompatible fragments, 
and every appropriateness in the association of the pieces, I conclude that 
they are portions of one and the same skeleton. The superior true molars 
